<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <title>伸缩容器、伸缩项目</title>
    <style>
        .outer {
            width: 700px;
            height: 300px;
            background-color: gray;

            /* 开启伸缩盒模型 */
            display: flex;
            margin: 0 auto;
            /* 单行 */
            /* 测轴起始点 */
            align-items: flex-start ;
            /* 侧轴结束点 */
            align-items: flex-end;
            /* 侧轴中心 */
            align-items: center;
            /* 基线 */
            align-items: baseline;
            /* 没高度的话充满侧轴高度 */
            align-items: stretch;

        }
        .inner1 {
            width: 80px;
            height: 80px;
            background-color: deeppink;
            box-sizing: border-box;
            border-width: 1px;
            border-style: solid;
            border-color: black;
           
        }
        .inner2 {
            width: 80px;
            height: 120px;
            font-size: 80px ;
            background-color: deeppink;
            box-sizing: border-box;
            border-width: 1px;
            border-style: solid;
            border-color: black;
           
        }
        .inner3 {
            width: 80px;
            height: 30px;
            background-color: deeppink;
            box-sizing: border-box;
            border-width: 1px;
            border-style: solid;
            border-color: black;
           
        }
        
       
    </style>
</head>
<body>
    <!-- 伸缩容器 -->
    <div class="outer">
        <!-- 伸缩项目 -->
        <div class="inner1">X</div>
        <div class="inner2">X</div>
        <div class="inner3">X</div> 
    </div>
</body>
</html>